SILVER MINING IN COLORADO. 613 



Average yield per ton, $109 08, coin. 



The works produced, under the management of previous owners, Gar- 

 rett, Martine & Company, about, or a little over, $20,000,^ coin, making a 

 total of $100,000 from their commencement to the date referred to above, a 

 period of something over two years. 



Concentration. — The high cost of metallurgical treatment added to that 

 of mining excludes from profitable working a large amount of second or third 

 class ore. The value of this varies from $20 or $25 to about $100 per ton, 

 for with the cost of reduction at $60, and an available yield of not more than 

 80 per cent, of the assay value, an ore must contain, under existing condi- 

 tions, at least 100 ounces of silver per ton, in order to pay all the expenses 

 of mining and milling and leave any margin of profit in the hands of the 

 producer. 



Although the veins about Greorgetown have produced some very rich 

 ores, it is probable that the amount of ore that can be worked profitably bears 

 but a small proportion to that which must remain unavailable without cheaper 

 methods of reduction. According to a statement on a preceding page, the 

 Terrible mine has produced about 200 tons of ore, yielding $200 and 

 upward per ton ; while the quantity of accumulated ore, of third class, 

 said to be worth about $80 or $100 per ton, is estimated at 1,200 or 1,500 

 tons. A ton of this ore, worth $80, which may represent the average value 

 of the w^hole, after paying $60 for milling, and aifording a net yield of 80 

 per cent., would leave the owners in debt for the expenses of handling, haul- 

 ing, and other items, including nothing of the costs of mining. If, however, 

 by some suitable and cheap method of concentration, the valuable mineral, 

 or a reasonably large part of it, contained in five or six or more tons of this 

 ore can be brought into one ton, the whole mass may be rendered available 

 for profitable working. 



It is probable that the proportion of low-grade ores to those of high 

 value is quite as great as the above, if not much greater, in the majority of 

 the Georgetown veins ; and the future prosperity of the district depends very 

 much on the success of the means adopted for concentrating or otherwise 

 rendering available the ores of the lower class ; for the business of any mine 



^ From statement furnished by Mr. Charles Martine. 



